Why so serious?: Underpants Run puts the fun in Ironman World Championship week

Julie Palmer dresses up as Wonder Woman for the 21st running of the Underpants Run on Thursday Palmer will be competing in her 22nd and final Ironman on Saturday. (Rick Winters/West Hawaii Today)
The 21st running of the Underpants Run took place down Alii Drive on Thursday. (Rick Winters/West Hawaii Today)
The 21st running of the Underpants Run took place down Alii Drive on Thursday. (Rick Winters/West Hawaii Today)
The 21st running of the Underpants Run took place down Alii Drive on Thursday. (Rick Winters/West Hawaii Today)
The 21st running of the Underpants Run took place down Alii Drive on Thursday. (Rick Winters/West Hawaii Today)
The 21st running of the Underpants Run took place down Alii Drive on Thursday. (Rick Winters/West Hawaii Today)
The 21st running of the Underpants Run took place down Alii Drive on Thursday. (Rick Winters/West Hawaii Today)
The 21st running of the Underpants Run took place down Alii Drive on Thursday. (Rick Winters/West Hawaii Today)
The 21st running of the Underpants Run took place down Alii Drive on Thursday. (Rick Winters/West Hawaii Today)
The 21st running of the Underpants Run took place down Alii Drive on Thursday. (Rick Winters/West Hawaii Today)
The 21st running of the Underpants Run took place down Alii Drive on Thursday. (Rick Winters/West Hawaii Today)
The 21st running of the Underpants Run took place down Alii Drive on Thursday. (Rick Winters/West Hawaii Today)
The 21st running of the Underpants Run took place down Alii Drive on Thursday. (Rick Winters/West Hawaii Today)

KAILUA-KONA — The Ironman World Championship is a serious competition where athletes from all over the world travel to the Big Island to challenge nature and the environment over the course of a 2.4-mile swim, 112-mile bike and 26.2-mile run from Kailua-Kona to Hawi.